The present invention relates to a volume hologram multilayer structure such as a volume hologram transfer foil or a volume hologram label which is stuck to a surface of an adherend such as a photograph or personal information attached to an identification card, an examination admission ticket, a passport, a certificate, or the like so as to form a transparent volume hologram for the purpose of ensuring security, and to a volume hologram seal in which a transparent volume hologram is formed on an adherend by using a volume hologram multilayer structure. The present invention relates to a counterfeit-proof volume hologram multilayer structure and a counterfeit-proof volume hologram seal making the replication of the volume hologram impossible.
Holography is a technology of recording both the amplitude content and the phase content of light waves reflected on a surface. A hologram made by this technology enables a representation of a three-dimensional image seen from different view points, differently from an ordinary photograph which contains an image seen from one view point only. The manufacture of holograms requires sophisticated technology and a complex and expensive apparatus. Accordingly, the counterfeit or alteration of hologram is generally difficult. Under favor of the difficulty in counterfeit, some attempts at using the holography as the counterfeit-proof means for identification cards, certificates, and the like had been executed.
While the sophisticated optical design technology and an expensive equipment are required for the hologram replication, the hologram replication is achieved by faying a photosensitive material for replication to a master hologram and irradiating the photosensitive material and the volume hologram with laser beam at the photosensitive material side. To cope with this, a counterfeit-proof volume hologram multilayer structure having a polarization control layer attached to one surface of a volume hologram thereof has been proposed (see Japanese Unexamined Patent Publication No. H6-138803). However, there is a problem that the polarization control layer is easy to be found.
It is an object of the present invention to provide a counterfeit-proof volume hologram multilayer structure and a counterfeit-proof volume hologram seal, capable of securely preventing the replication of a volume hologram recorded therein even if a counterfeiter attempts to replicate the volume hologram recorded in the volume hologram multilayer structure or the volume hologram seal as a master.